Track-laying tractor



June '26, 1328.

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C. L. BEST TRACK LAYING TRACTOR Filed Sept. 28, 1925 5 Sheets-Sheet 5 atent STATES auri CLARENCE LEO BEST, OF SAN LEANDRO, CALIFORNIA, ASSIGNOR T0. GATEBPELQB CTOR 00., OF SAN LEANDRO, CALIFORNIA, A CORPORATION OF CALIFORNIA.

TRACK-LAYING- memos.

' Application filed September as, 1925. serial No. 59,169.

This invention relates to improvements in track laying tractors, and more particularly to improved safety idler holding and automatic track tensioning means.

A serious difficulty in the operation of track laying tractors over sandy soil, gravel or sticky mud, is that the sprockets and tracks become plugged with hard packed dirt and tremendous tension is put on the tracks and associated parts, resulting in serious damage to the machine, the breaking of the front idler boxes or the tracks,

the distortion of the truck frames, and cause 'ing disengagement of the tracks from the wheels. It has heretofore been proposed to employ tensioning means in the form of springs interposed between abutmen-ts on the frame and the idler boxes and forcing the same forwardly with a yielding-pressure, but such constructions are not practicable for the reason that while upon forward movement the pull on the front idler wheel is slight, upon backward movement the pull ing action is against the front idler, forcing the same back against the pressure of the springs and slackening the track.

The object of the present inventionis to overcome the dilfieulty referred to; to pro vide improvedidler holding and automatic track tensioning means of a simple, eflicient nature that will yield when the track is subjected to undue strain permitting the idler wheel bearing to move back and relieve the parts of strain; that will automatically move the idler bearing forward to tighten the track as the excessive strain on the track is relieved, and which, at the same time, will always maintain the track at the proper tension, in backing up as .well as during forward movement.

The invention with other objects and ad vantages thereof, and the particular construction,..combination and arrangement of parts comprising the same will be understood from the hereinafter contained detail description, when considered'i n connect on with the accompan ing draw ngs forming part hereof, and ilustrating one embod1 ment of the invention. v

' In the drawings:

Figure 1 is a side elevation of a tractor truck equipped with safety idler holding the invention.

shown 109 automatic track tensioning means inaccordance with the present invention.

Fig. 2 is a detail section, on the line 22 frame members of the truck being shown in section. I

Fig. 7 is a detail top plan view of one of the idler shaft bearing boxes and the fric- 'tion brake associated therewith.

Fig. 8 is a detail side elevation, with parts shown in section, of the idler shaft bearing box structureillustrated in Figure 7.

The invention contemplates improved safety idler holding and automatic track tensioning means including spring pressure tensioning means in combination with a frictlon brake for retarding the movement of e the idler box, and whichacting in conjunction with the spring tensioning means, will maintain the idler in operative position with the track under proper tension when the tractor is backing up under full power, while at the same time, being adapted to yieldper- .mitting the idler bearing to move back to relieve excessive strain, as when the parts 35 become plugged with dirt, and to move. up the idler bearing to maintain the track tight'as the dirt works free from the track and sprocket.

While a preferred embodiment of the invention is illustrated in the drawings, it will of course be understood that changes and variations in the particular construction shown, and the embodiment of the inventionin other forms, as will appeal to those skilled in the art and falling within the scope of the appended claims, may be prac ticed without departing from the spirlt of In the drawings, the invention is applied to one of the well known forms of tractor trucks,- the same comprising spaced parallel channels 1 suitably secured together, an endless tread 2, a rear driving sprocket 3.

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mounted in bearings 4 fixedl secured tothe channels-1, and a 'front 1 ler surface or plate part 12 having 'a flat bottom face to engage the upper face of the upper flange 1 of'one of the channels 1, with a portion 13 at its inner side to fitaganst the inner side of .the channels '1, and at its other side, an extension 14 extending around and under the upper flange 1 of the channel to hold the box 10 thereon against lateral displace- .ment while permitting the same to slide thereon (see artic-ularly Figures 2 and 6 of the drawings In the particular exemplification of the invention illustrated in the drawings, the portion 13 at the inner side of the bottom plate 12 of the box 10 is formed by'thelower part of an inner annular flangeorcollar 15 which is adapted to fit over a hub part5? of the idler wheel 5. The extension 14 takes the form of a separate plate member detachably connected to the main part of the axle box 5 by bolts and nuts 16, 17, the bolts 16 extending vertically through openings in the bottom plate part 12 and bosses 18 on the upper side thereof.-' a p The yieldable idler holding and track tensioning means includes coiled springs 19, each spring being interposed between and bearing at opposite ends against a depending lug 20 on one of the axle boxes 10, and an abutment '21 on one of the truck frame channels 1, and being supported on a rod 22 which at one end slidably engages an aperture 23 in the depending lug 20, and at its other end has an adjustable threaded n connection with the abutment 21. Each abutment 21 is shown in the form of a bracket suitably secured to one of the channels 1 by bolts and nuts '24, 25, or equivalent means, and having an outstandingabutment part in the form of a split nut 21 pro- 7 ends thereof, the tension o vided with a clamp screw 21", the rods 22 each having at one end a threaded orti'on 22 adjustably engaging one of the sp it nuts 21. As will be understood by turning the rods 22 through the heads 22 on the outer the springs 19 can beadjusted.

Each of the idler axle boxes 10 is provided with friction brake mechanism to cooperate with the spring pressure mechanism to yieldably hold the boxes in place, said friction brake mechanism operating against a new-1,817

surface of the truck frame channels 1. Each journal boxlO is shown provided with a pair of friction brake devices located thereon near the ends of the fiat plate part 12 thereof at either side of the cylindrical journal part 11. Each friction brake de vice comprises a spring pressed brake element engagng the upper face of the upper the coiled springs 27 abut. The brake elemcnts 26, which take. the form of circular plates, may be constructed of mild steel or other material suitable for the purpose.

The friction brake mechanism of the idler bearing boxes 10 is adapted to exert sufiicient retarding or braking force to maintain the idler box in position with the track under proper operative tension when the tractor is backing up under full power. If the track plugs it must plug so tight that it comes under tension of several thousand pounds before it overcomes the friction brake mechanism and the tension of the springs 19.

At this stage, the front idler wheel 5 snaps back and relieves the excessive strain or tension. Under these circumstances while the excessive strain and tensionis relieved, the track is maintained tight and operating in this wa the tendency is for the track to free itseif of the dirt, and as soon as this takes place, the front idler snaps forward to maintain the track tight.

It will be noted that the friction brake mechanism operating in conjunction with the spring pressure means affords idler holding and automatic track tensioning means of a simple, efficient nature providing for maintaining the track under proper operative" tension on backing up under full power as" well as upon forward movement, and, at the same time, provides for yielding or backward movement of the idler wheel to relieve the parts of undue strain when the track becomes plugged with dirt.

What I claim is:

1. In a track laying tractor, a truck frame, an endless track, a drivingsprocket and an idler for the track, a bearing for the idler slidably mounted on the frame, and yieldable means for holding the said idler bearing in place on the frame, said means including spring tensioning means in combination with;

a friction brake. v

2. In a track laying tractor, aj truck frame, an endless track, a driving sprocket and an idler, for the track, a bearing for the idler 'slidably mounted on the frame, and yieldable means for hoiding the said idler bearing no i oreen? in place on the frame, said means including spring tensioning means in combination with a friction brake, said friction brake comprising a spring pressed brake element on the idler bearing arranged to engage a part of the truck frame.

3. In a track laying tractor, a truck frame, an endless track, a driving sprocket and an idler for the track, a bearing for the idler slidably mounted on the frame, and yieldable means for holding the said idler bearing in place on the frame, said means including spring tensioning means in combination with a friction brake, said friction brake comprising a chamber on the idler bearing open at one end at the bottom face of the bearing, a brake block slidable in the lower end of said chamber, and a coiled spring in the chamber back of said block pressing the same against a part of the truck frame.

4. In a track laying tractor, a truck frame, an endless track, a driving sprocket and an idler for the track, journal boxes for the idler Wheel slidably mounted on the frame, yieldable means for holding the idler wheel journal boxes in place on the frame, said means including a coiled spring associated with each of the journal boxes to press the same forwardly, and a. spring pressed friction brake device on each journal 1002: arranged to engage a part of the frame,

5. In a track laying tractor, a truck frame, an endless track, a. driving sprocket and an idler Wheel for the track, journal boxes for the idler wheel slidably mounted on the frame, yieldable means for, holding the idler journal boxes in place on the frame, said means including a coiled spring associated with each of the journal boxes to press the same forwardly, and a pair of spring pressed friction brake devices located on each journal box near either end thereof and arranged to engage a part of the frame.

6. Ina track laying tractor, a truck frame, comprising spaced parallel bars each having a lateral flange, an endless track, a driving sprocketand idler Wheel for the track, journal boxes for the idler wheel each slidably mounted on the flange of one of the frame bars at the upper side thereof and having an extension part to slidably engage the flange at the under side thereof; and yieldable idler holding and track tensioning means including coiled springs to exert pressure longitudinally upon the idler journal boxes, in combination with a. friction brake for each idler journal box comprising a brake element arranged to engage the flange of one of the frame bars at the up er side thereof, and a sprin interposed tween the brake element an a part on the idler journal box and ressing the brake element downwardly against the upper face of the flange.

In testimony whereof I hereunto aifix my signature.

CLARENCE Lno BEST. 

